The disclosures of Japanese Patent Applications Nos. 2001-321040 filed on Oct. 18, 2001 and 2002-148330 filed on May 22, 2002, each including the specification, drawings and abstract, are incorporated herein by reference in their entireties.
1. Field of the Invention
The invention relates to an automatic transmission provided between an engine and a drive wheel in vehicles such as motor vehicles, railway vehicles, etc.
2. Description of the Related Art
Many vehicles adopt planetary gear-type multi-speed transmissions suitable for selecting an appropriate speed from a plurality of predetermined transmission speed ratios or gear speeds. With regard to such planetary gear-type multi-speed transmissions, it is desirable that the construction be simple and small in size, and that a great range of transmission gear ratios and speeds be allowed, and that the selectable transmission gear ratios change in a geometric progression or a similar fashion.
Planetary gear-type multi-speed transmissions capable of shifting speeds in seven steps have been proposed. Examples of such transmissions are planetary gear-type multi-speed transmissions in the third embodiment (FIGS. 5 and 6) and the fourth embodiment (FIGS. 7 and 8) in Japanese Patent Application Laid-Open No. 2000-266138. These transmissions allow great ranges of transmission gear ratios and speeds. However, since the transmissions substantially adopt four sets of planetary gear units, the transmissions have drawbacks of increased lengths and therefore degraded vehicle installability.
It is an object of the invention to provide an automatic transmission that allows an increased range of transmission gear ratios or speeds.
A first aspect of the invention relates to a type of automatic transmission that changes rotational speed of an input rotatable element in a stepwise manner and outputs rotation of an output rotatable member. This automatic transmission has a first planetary gear unit, a second planetary gear unit, and a third planetary gear unit. Where five rotatable elements formed based on interconnection of some of a first sun gear, a first carrier and a first ring gear of the first planetary gear unit, and a second sun gear, a second carrier and a second ring gear of the second planetary gear unit, and a third sun gear, a third carrier and a third ring gear of the third planetary gear unit are termed a first rotatable element, a second rotatable element, a third rotatable element, a fourth rotatable element, and a fifth rotatable element from an end toward another end in an alignment graph that indicates rotational speeds of the five rotatable elements, the first to fifth rotatable elements are arranged as follows. The first rotatable element is selectively connectable to the input rotatable element via a second clutch, and is selectively connectable to a non-rotatable member via a first brake. The second rotatable element is selectively connectable to the non-rotatable member via a second brake. The third rotatable element is selectively connectable to the input rotatable element via a first clutch, and is selectively connectable to the non-rotatable member via a third brake, and a portion of the third rotatable element connected to the first clutch and the third brake is selectively connectable to another portion of the third rotatable element via a third clutch. The fourth rotatable element is connected to the output rotatable member. The fifth rotatable element is selectively connectable to the non-rotatable member via a fourth brake. This automatic transmission establishes gear speeds as follows. Engagement of the second clutch, the third brake and the fourth brake establishes a first gear speed having a greatest transmission gear ratio. Engagement of the second clutch, the third clutch and the fourth brake establishes a second gear speed of a transmission gear ratio that is smaller than the transmission gear ratio of the first gear speed. Engagement of the first clutch, the second clutch and the fourth brake establishes a third gear speed of a transmission gear ratio that is smaller than the transmission gear ratio of the second gear speed. Engagement of the first clutch, the third clutch and the fourth brake establishes a fourth gear speed of a transmission gear ratio that is smaller than the transmission gear ratio of the third gear speed. Engagement of the first clutch, the second clutch and the third clutch establishes a fifth gear speed of a transmission gear ratio that is smaller than the transmission gear ratio of the fourth gear speed. Engagement of the first clutch, the third clutch and the first brake establishes a sixth gear speed of a transmission gear ratio that is smaller than the transmission gear ratio of the fifth gear speed. Engagement of the first clutch, the third clutch and the second brake establishes a seventh gear speed of a transmission gear ratio that is smaller than the transmission gear ratio of the sixth gear speed.
Therefore, the provision of the three planetary gear units, that is, the first planetary gear unit, the second planetary gear unit and the third planetary gear unit, achieves as broad a range of gear ratios as sevenforward speeds. Hence, it is possible to provide a small-size vehicular planetary gear type multi-speed transmission capable of achieving good high-speed running performance and good uphill starting performance.
A second aspect of the invention relates to a type of automatic transmission that changes rotational speed of an input rotatable element in speed in a stepwise manner and outputs rotation from an output rotatable member. This automatic transmission has a first planetary gear unit, a second planetary gear unit, and a third planetary gear unit. Where five rotatable elements formed based on interconnection of some of a first sun gear, a first carrier and a first ring gear of the first planetary gear unit, and a second sun gear, a second carrier and a second ring gear of the second planetary gear unit, and a third sun gear, a third carrier and a third ring gear of the third planetary gear unit are termed a first rotatable element, a second rotatable element, a third rotatable element, a fourth rotatable element, and a fifth rotatable element from an end toward another end in an alignment graph that indicates rotational speeds of the five rotatable elements,, the first to fifth rotatable elements are arranged as follows. The first rotatable element is selectively connectable to the input rotatable element via a second clutch. The second rotatable element is selectively connectable to a non-rotatable member via a second brake. The third rotatable element is selectively connectable to the first rotatable element via a fourth clutch, and is selectively connectable to the non-rotatable member via a third brake, and is selectively connectable to the input rotatable element via a first clutch. A portion of the third rotatable element connected to the fourth clutch and the third brake and a portion of the third rotatable element connected to the first clutch are selectively connectable to each other via a third clutch. The fourth rotatable element is connected to the output rotatable member. The fifth rotatable element is selectively connectable to the non-rotatable member via a fourth brake. This automatic transmission establishes gear speeds as follows. Engagement of the second clutch, the third brake and the fourth brake establishes a first gear speed having a greatest transmission gear ratio. Engagement of the second clutch, the third clutch and the fourth brake establishes a second gear speed of a transmission gear ratio that is smaller than the transmission gear ratio of the first gear speed. Engagement of the second clutch, the fourth clutch and the fourth brake establishes a third gear speed of a transmission gear ratio that is smaller than the transmission gear ratio of the second gear speed. Engagement of the first clutch and the fourth brake establishes a fourth gear speed of a transmission gear ratio that is smaller than the transmission gear ratio of the third gear speed. Engagement of at least three of the first clutch, the second clutch, the third clutch and the fourth clutch establishes a fifth gear speed of a transmission gear ratio that is smaller than the transmission gear ratio of the fourth gear speed. Engagement of the first clutch, the second clutch and the third brake establishes a sixth gear speed of a transmission gear ratio that is smaller than the transmission gear ratio of the fifth gear speed. Engagement of the first clutch and the second brake establishes a seventh gear speed of a transmission gear ratio that is smaller than the transmission gear ratio of the sixth gear speed.
Therefore, the provision of the three planetary gear units, that is, the first planetary gear unit, the second planetary gear unit and the third planetary gear unit, achieves as broad a range of gear ratios as seven forward speeds. Hence, it is possible to provide a small-size vehicular planetary gear type multi-speed transmission capable of achieving good high-speed running performance and good uphill starting performance.
A third aspect of the invention relates to a type of automatic transmission that changes rotational speed of an input rotatable element in a stepwise manner and outputs rotation from an output rotatable member. This automatic transmission has a first planetary gear unit, a second planetary gear unit, and a third planetary gear unit. Where five rotatable elements formed based on interconnection of some of a first sun gear, a first carrier and a first ring gear of the first planetary gear unit, and a second sun gear, a second carrier and a second ring gear of the second planetary gear unit, and a third sun gear, a third carrier and a third ring gear of the third planetary gear unit are termed a first rotatable element, a second rotatable element, a third rotatable element, a fourth rotatable element, and a fifth rotatable element from an end toward another end in an alignment graph that indicates rotational speeds of the five rotatable elements, the first to fifth rotatable elements are arranged as follows. The first rotatable element is selectively connectable to the input rotatable element via a second clutch, and is selectively connectable to a non-rotatable member via a first brake. The second rotatable element is selectively connectable to the non-rotatable member via a second brake. The third rotatable element is selectively connectable to the first rotatable element via a fourth clutch, and is selectively connectable to the non-rotatable member via a third brake, and is selectively connectable to the input rotatable element via a first clutch. A portion of the third rotatable element connected to the fourth clutch and the third brake and a portion of the third rotatable element connected to the first clutch are selectively connectable to each other via a third clutch. The fourth rotatable element is connected to the output rotatable member. The fifth rotatable element is selectively connectable to the non-rotatable member via a fourth brake. This automatic transmission establishes transmission gear speeds as follows. Engagement of the second clutch, the third brake and the fourth brake establishes a first gear speed having a greatest transmission gear ratio. Engagement of the second clutch, the third clutch and the fourth brake establishes a second gear speed of a transmission gear ratio that is smaller than the transmission gear ratio of the first gear speed. Engagement of the second clutch, the fourth clutch and the fourth brake establishes a third gear speed of a transmission gear ratio that is smaller than the transmission gear ratio of the second gear speed. Engagement of the first clutch and the fourth brake establishes a fourth gear speed of a transmission gear ratio that is smaller than the transmission gear ratio of the third gear speed. Engagement of at least three of the first clutch, the second clutch, the third clutch and the fourth clutch establishes a fifth gear speed of a transmission gear ratio that is smaller than the transmission gear ratio of the fourth gear speed. Engagement of the first clutch, the third clutch and the first brake establishes a sixth gear speed of a transmission gear ratio that is smaller than the transmission gear ratio of the fifth gear speed. Engagement of the first clutch and the second brake establishes a seventh gear speed of a transmission gear ratio that is smaller than the transmission gear ratio of the sixth gear speed.
Therefore, the provision of the three planetary gear units, that is, the first planetary gear unit, the second planetary gear unit and the third planetary gear unit, achieves as broad a range of gear ratios as seven forward speeds. Hence, it is possible to provide a small-size vehicular planetary gear type multi-speed transmission capable of achieving good high-speed running performance and good uphill starting performance.